About metrology

About metrology

Metrology is the science of measurement. Since 1960, the basis for measurement has been officially formed by the SI unit system (SI stands for Système Internationale), otherwise called the metric system. In a measurement there is always a comparison between an unknown quantity with a quantity whose properties are known (standard or reference material) and taking into account the measurement uncertainty.

Measurements and the global energy challengeThis video shows why it is important to keep a close eye on the use of energy and the vital role that measurements play in this global challenge.

International agreements: SI systemIn international trade it is necessary that we measure with the same dimensions. A bolt manufactured in one country would otherwise never fit on a nut from a different country. Thanks to the SI system measurement is done nationally and internationally with the same dimensions. The unit system defines seven basic SI units, namely: the second (time), the metre (length), the kilogram (mass), the kelvin (temperature), the candela (light intensity), the mol (quantity of substance) and the ampere (electrical current).

These are fundamental units for physical quantities, that were accepted and recommended by the general conference on weights and measures (Conférence Générale des Poids et Mesures, CGPM). All other SI units can be derived from these basic units.

Via the Mutual Recognition Arrangement (MRA), signed by many countries in 1999, it was agreed that the countries would accept each other’s national standards and associated measurement results.

Traceable measurementIn order to be able to compare together measurements that are conducted in different places or at different times, the measurements must be traceable. Running a new world marathon record can only be established if the measurements are mutually comparable. The same applies, for example, to the emission of greenhouse gases: if there are agreements on the emission per country, the measurements must be made in the same way to allow conclusions to be drawn.

The traceability to the primary standard is regulated via the National Metrology Institutes (NMIs). They manage the national measurement standards that are compared to each other internationally. In the Netherlands, VSL is responsible for this. Traceability is regulated by calibrating means of measurement.

Metrology as a requirement for innovative developmentsCompanies and society as a whole are continuously in development. New technologies are introduced and measurements are almost always important to them. Consider the accurate irradiation of cancer, the developments in nanotechnology, and the generation and transportation of energy. These developments cause a demand for ever-higher accuracy and dependability of existing standards.

For example, because of the possibility to deal on stock exchanges online (via software), the time stamp, in other words the ‘second’ has become crucial to the success of a transaction. New developments demand new measurement standards. For the development of LNG (Liquefied Natural Gas) for example, it is necessary that a primary standard is developed for the measurement of this extremely cold fuel. In the Netherlands, VSL manages and develops the national measurement standards by commission of the Dutch government.

Overview of the European research studies in which VSL is participating.

The Metrology ActIn the Netherlands, the rules for measurement are stipulated in the Metrology Statue (2006) (in Dutch). This defines matters including the management and development of standards (the Ministry of Economic Affairs has stipulated in a contract that VSL will take responsibility for this). The requirements that are imposed on means of measurement that are used for example in transactions (weighing scales, petrol pumps, energy meters, etc.) are also defined in the Metrology Statue, so that both the consumer and supplier are protected against erroneous measurements.